An Electronic Article Surveillance (EAS) system is designed to prevent unauthorized removal of an item from a controlled area. A typical EAS system may comprise a monitoring system and one or more security tags. The monitoring system may create an interrogation zone at an access point for the controlled area. A security tag may be fastened to an item, such as an article of clothing. If the tagged item enters the interrogation zone, an alarm may be triggered indicating unauthorized removal of the tagged item from the controlled area. In general, the security tag must be deactivated before a tagged item can leave the controlled area without triggering the alarm.
Security tags may take a variety of forms including soft tags and hard tags. In general, soft tags are disposable and used only once, while hard tags are reusable. An example of a soft tag is an adhesive-backed security label. A soft tag may be deactivated by a deactivator unit, such as a scanner that uses a specific field to deactivate the soft tag when it touches or comes in close proximity to the soft tag.
Hard tags typically comprise a plastic tag body housing an EAS sensor and a locking mechanism including a pin or tack which passes through the item and is clamped to the tag body to secure the item and tag together. In general, a hard tag requires a detacher unit to remove the tack from the tag body and allow the item to be separated from the hard tag. In some applications, a detacher unit may include a magnet assembly which applies a magnetic field to the tag body for releasing the tack.
FIG. 1 illustrates a conventional hard tag 10 having a plastic tag body 11 formed with a protrusion 12. The tag body 11 houses an EAS sensor 13 for triggering an alarm. The hard tag 10 includes a tack 14 with an enlarged head 15. As shown, the tack 14 is securely held by a clamping mechanism 16 within the tag body 11.
FIG. 2 illustrates a conventional magnet assembly 20 for a detacher unit. The magnet assembly 20 includes a cylindrical magnet 21 and an oppositely magnetized ring magnet 22 stacked on top of the cylindrical magnet 21. As shown, the magnet assembly 20 includes a cavity 23 of approximately 6 to 7 mm in depth. This configuration is well-suited for a conventional hard tag, such as hard tag 10, where the cavity 23 of the magnet assembly 20 is compatible with the protrusion 12 of the tag body 11. To permit the removal of the tack 14, the protrusion 12 is inserted into the cavity 23 to take advantage of the strong field inside the ring magnet 22. The magnet assembly 20 provides a substantially vertical magnetic field in the cavity 23 sufficient to force the clamping mechanism 16 to disengage and allow removal of the tack 14 from the tag body 11.
In many tagging applications, such as tagging of bottles and compact discs, for example, the clamping mechanism of a hard tag may be embedded in the existing packaging of an item or may have a low profile to minimize vulnerability of defeats and facilitate shelving of items. For such applications and packaging requirements, a different detacher design is required to provide open access to the embedded or low profile clamping mechanism and, at the same time, providing a sufficient magnetic field.